This will improve the user experience on Android TV devices,
see bug for details.
In addition when connecting adb to the device by ethernet
for cts, wifi will not connect, causing lots of tests to fail.
For example:
[CTS7.1]android.net.wifi.cts.WifiInfoTest#testWifiInfoProperties
[CTS7.1]android.net.cts.ConnectivityManagerTest#testConnectivityChanged_
manifestRequestOnlyPreN_shouldReceiveIntent
Use command:settings to put global wifi_data_always_on 1 to enable it.
Bug: 26102779
Test: Manual, CTS.
Change-Id: I711d93061a6bc7164d98a858912f781e1b967406
838c66128f